Molded plastic fuse construction



Feb. 19, 1946.

G. w.' WIARD 2,395,206

MOLDED PLASTIC FUSE CONSTRUCTION Filed July 17, 1943 2 Sheets-Sheet 1 awe/rm 7. W T I Hrd Feb. 19, 1946. G. w. NIARD MOLDED PLASTIC FUSE CONSTRUCTION Filed July 17, 1945 2 Sheets-Sheet 2 Patented Feb. 19, 1946 UNITED STATES PATENT OFFICE' 2,395,206 MOLDED PLASTIC FUSE CONSTRUCTION George W. Wiard, Keswick, Va., assignor to Virginia Electric Manufacturing Corporation, Charlottesville, Va., a corporation of Virginia Application July 17, 1943, Serial No. 495,161

4 Claims.

This invention relates to the manufacture of fuses and particularly fuses of the knife blade type. It has for its object to provide a plastic molded casing for enclosing the fuse link and anchoring and supporting the knife blades.

According to variants within the scope of the invention, the casing may be molded in sections and fabricated with the link unit, or molded unitarily therewith.

The invention relates to fuse construction within the bounds of thi inventive concept.

Other objects of the invention will appear as the following description of several embodiments thereof proceeds.

In the drawings which accompany and form a part of the following specification and throughout the several figures of which the same reference characters have been used to denote identical parts:

Figure 1 is a longitudinal sectional view of a fuse casing divided in a longitudinal plane perpendicular to the fiat dimension of the knife blades:

Figure 2 is a longitudinal section taken in a plane perpendicular to the section plane of Figure 1;

Figure 3 is a cross-section taken along the line 3-3 of Figure 1; I

Figure 4 is a fragmentary perspective view of one-half of the divided casing;

Figure 5 is a longitudinal view in elevation showing one of the identical halves of a molded fuse casing in another vention;

Figure 6 is a longitudinal section in a plane perpendicular to that of Figure 5;

Figure 7 is a cross-section taken along the line I4I4 of Figure 6.

Referring now in detail to the several figures, and first adverting to that formof the invention shown in the group of Figures 1 to 4, inclusive, the fuse link unit comprises the longitudinally spaced knife blades l and 2 with the intervening fusible link 3 secured at its ends thereto. The middle portion of the link 3 is narrowed as at 4 by the provision of the lateral indentations 5, which is conventional in the art.

A plastic casing 6 surrounds the fuse link 3 and the adjacent ends of the knife blades I and l, defining a chamber 1 about the fuse link which nay be air filled, contain any suitable inert gas, :r be filled with a powdered heat diffusing sub- :tance, as may be desired.

Since the plastic casing 6 may be transparent, t i preferred to have the chamber 1 either air modification of the inappears as a single long line when or gas filled so that the condition of the link may be readily observed. In order that its condition may be made visible in the dark, the fuse link may be coated with a stripe 8 of paint, which is luminous in the dark, extending acros the narrow portionof the link and for some distance therebeyond in both directions. Such a stripe the fuse is intact, and as a broken line when the fuse is blown. Inasmuch as the knife blades are generally arranged perpendicular to the fuse panel, it is preferred to have the stripe of luminous paint applied to the edge of the fuse link, where it will be visible when viewed from a forward direction with respect to the fuse panel.

The casing 6 is preferably formed of premolded longitudinally divided halves 9 and I 0, one of which is shown in perspective in Figure 4. These halves are divided in a diametrical plane perpendicular to the fiat sides of the knife blade. Each half is provided at it opposite ends with a semi-head ll formed with a slot l2 of such length and width as to snugly embrace one-half of the adjacent knife blade. The knife blades are provided with the diametrically opposite indentations l4 and I5 and the casing halves 9 and 10 with the integrally molded lugs I6 at the ends of the slots l2, which interdigitate with the indentations l4 and I5 and securely anchor the knife blades in position.

The longitudinal edges l1 and I8 of the respective casing halves are formed with stepped joints, as shown, whereby one automatically interfits with the other when the two are placed in juxtaposition in assembly, without the necessity of any particular precision in their allocation. The interfitting of the lug I6 into the respective recesses l4 and I5 assures that the casing halves will be assembled with their ends flush in the same plane.

The surfaces of the stepped longitudinal joints are preferably moistened with a volatile solvent for the plastic of which the casing halves are made so that upon evaporation of this solvent the two halves of the casing are autogenously joined.

Now referring to that form of the invention shown in Figures 5 and 7, the head construction is similar to that shown in Figure 1 in that there is a slot 38 in each head to receive the knife blade and having lugs 39 extending inwardly from the ends of said slot interfitting with recesses 40 formed in the knife blade. In the interest of strengthening the heads adjacent the respective knife blades, the undersides of said heads are provided with the flanges 4| bordering the sides of 2. the slots 38. The sidewalls of the casing are also thickened at diametrically opposite points by the grooved ribs 42, which extend longitudinally to the inner ends of the knife blades, the grooves of said ribs snugly receiving the lateral marginal portions of said knife blades. This adequately strengthens the fuse construction against the sometimes. severe stresses imposed upon the fuse when the. knife blades; are inserted in the clips of the fuse panel.

The casing is preferably molded in two identical halves, 43 and 44, which are joined in a longitudinal plane perpendicular tothelongitudlnal plane of the slot 38. The wallsof the casing are thickened, as indicated at 45 and 46,.longitudinally in a region intersected by theplaneof juncture of the two halves so as to increase the area of the faces of the joint sufficiently' to make the joint at least as strong as the rest of the wall structure. of each. half are provided, one. with a ridge 4:1 and the. other with a. groove 43:, said ridge. and said groove being of. equal length andzt'elminating equal distances from being. of complementary cross sectional contour throughout, whereby said halves when. put to' getherv register. in. flushv congruency through. the matching. of the ridge and groove of one half: with the groove. and ridge of the. other.-., The: two halves are cementitiously united. throughout'their plane of juncture; The; fact. that the. halves, of the fuse casing in identicalin all particulars; enables bothhalveseto bemade in the same: mold.

While I have in the above. description: disclosed what I believe tobe preferred and practicalexnbodiments of the invention, it will be; understood to those skilledin the art that the details of con.-

struction and. the arrangement of parts as shown:

and describedare. by way of example; and not to be construed as. limiting the scope of the invention. as defined in the appendedclaims.

What I claimas my inventionzis;

1. Electrical fuse construction comprising a; link unit. consisting of spaced flat knife blades with an intervening flat fusible linkrigidly fixed thereto with the flat sides of said link and blades in'parallelplanes; said'blades. having recesses extending inward from opposite lateral edges, a hollow molded casing of insulation material surrounding said link and the adjacentends of said knifeblades, said casing having. ends formed with transverse. slots snugly fitting about said. blades in the zone. of said recesses, through. which slots said. blades extend, the end Walls of said slots in.- a.

terfitting with said recessesto hold. said. blades longitudinally immovable, said. casing being lon- The opposite longitudinal joint faces the. ends, of the; casing and:

this: form of the invention are.-

knife blades, said casing gitudinally divided in a plane perpendicular to the flat side of said link unit whereby in assemblage, the parts of said casing may be pressed into tight engagement with the lateral edges of said blades, said parts being cementitiously united.

2. Electrical fuse construction comprising a link unit. consisting. of spaced. flat knife blades with an intervening fiat fusible. link rigidly fixed thereto with the flat sides of said link and blade in parallel planes, said blades having recesses extending inward from opposite lateral edges, a hollow molded casing of insulation material surrounding said link and the adjacent ends of said having ends formed with transverse slots snugly fitting about said blades, through which slots said blades extend, the end walls of said slots being formed with inwardly extending lugs, spaced from the planes which bound the opposite faces of said slots, said lugs interfitting with said recesses to hold said: blades immovable, said. casing beinglongitudinally divided in a; plane perpendicular to the fiat sideof' said. link unit, whereby in assemblage, the parts of said. casing may be pressed into tighttengage ment with the lateral edges of said blades; sa d parts being cementitiously united.

3;. Electrical. fuse construction comprising a link unit consisting of spaced flat knife bladesl with an intervening fiat fusible. link rigidly fixed thereto withthe flat sides of said link and blades in. parallel. planes, said: blades havingv recesses extending'inward from opposite-lateral edges, a hoilow molded casing of insulation material. surroundingsaid link and; the. adjacent ends of said knife'blades, said casing having ends formed with transverseslots snugly fitting about saidblades inthe zone. of said recesses; through which slots saiid'v blades extend, the end walls of said slots intemtv ting. with said: recesses tohold said bladeslongitudinally immovable, being formed with diametrically opposite longitudinal slots snugly receiving the opposite lateral.

edges-of said blades in the zone. of union. between said blades and link, said casing; being longitudinally divided in a plane perpendicular to: the flat side of said link unit whereby in assemblage, the parts of said casing may be pressed into-tight engagement withthe lateraledges of said blades, said parts being cementitiousiy. united.

4. Electrical fuse construction as claimed. in claim 3, the. longitudinal. meeting faces of the parts of said divided casing being formed on. one.

side with a longitudinal feather and on the 0990;- site side. with a complementary feather receivin channel.

GEORGE. W. W'IARD.

the side Walls of said casing; 

